Apparatus for supporting a helical delay line in a traveling wave tube in a substantially nonloading manner



April 14. 1970 H. BITTORF Hm. I 3,506,872

APPARATUS FOR SUPPORTING A HELICAL DELAY LINE IN TRAVELING WAVE TUBE IN A SUBSTANTIALLY NONLOADING MANNER Filed April 11, L967 2 Sheets-Sheet 1 Fig.1

BYJQJ/J ATTORNEYS Aprll 14. 1970 H BITTORF ETAL 3,506,872

APPARATUS FOR SUPPORTING A HELICAL DELAY LINE IN TRAVELING WAVE TUBE IN A SUBSTANTIALLY NONLOADING MANNER Filed April 11. 196 2 Sheets-Sheet 2 INVENTORS MA /woke BHMQF, E404 A m/z. bw/e545 fl/a/ssl-zocb flame/cu Ar/wsog Al L A/gye ,e 4 Mae/v52 5154 2 I K 2 AITORNLYA United States Patent Office 3,506,872 Patented Apr. 14, 1970 Int. Cl. H1 /34 US. Cl. 3153.5 3 Claims ABSTRACT OF THE DISCLOSURE A traveling wave tube utilizing a delay line in the form of a helix, in which the helix is supported by a plurality of insulating bars extending parallel to the helix axis, which bars may bear directly upon the inner wall surface of the vacuum casing coaxially enclosing the helix, such bars being of hollow tubular formation, and preferably provided with transversely extending slots disposed between contact surfaces of the helix.

The invention relates to a traveling wave tube utilizing a helix as delay line which is mounted between at least three insulating bars extending parallel to the helix axis.

Traveling wave tubes of the general type here involved are already known, for example, from Patent No. 2,922,067. It is also known from this patent to reduce the dielectric strain of the helix created by the insulating bars by the utilization of ceramic bars which possess a longitudinal groove along the helix. In this manner, the ceramic bars present a crescent-like profile, with the helix nesting upon the two knife-like edges thereof.

In the described, known helix mounting, the provision of the dielectric mounting bars with a longitudinal groove influence the mechanical and thermal rigidity of the retaining bars. There is, in particular, the danger of breaking olf the narrow knife edges upon which the helical delay line rests. Apart from this, the formation of such a longitudinal groove is limited practically only to ceramic retaining bars.

It is the object of the invention to construct the mounting of a helix with dielectric longitudinal bars in such a manner that the dielectric load of the helix line remains small, and at the same time avoiding technological difficulties. In order to solve this problem it is proposed, according to the invention, in the case of a traveling wave tube, of the type initially mentioned, that the insulating bars be tubular. In this case the insulating tubes preferably may be provided with opening in the tube wall which are axially spaced and are disposed between successive surfaces of the helix disposed in contact with a tube.

A traveling wave tube according to the invention has the advantage of a high coupling resistance as the dielectric load of the helix line is strongly reduced in comparison with solid, unnotched insulating bars, resulting from the small space factor of the. insulating bars. The helix mounting with its insulating tubes is, however, mechanically as stable as a mounting utilizing solid bars. Likewise, there is no limitation to a specific material for the insulating tubes because ceramic material as well as quartz or glass can be readily produced in tubular form without difiiculties.

The invention will be explained in greater detail in con nection with the drawings, wherein like reference numerals indicate like or corresponding parts, and in which:

FIG. 1 is a longitudinal section of a traveling wave tube according to the invention;

FIG. 2 is a transverse cross section of the tube illustrated in FIG. 1;

FIG. 3 is a longitudinal section, similar to FIG. 1, illustrating a further embodiment of the invention;

FIG. 3a is another illustration of the apparatus of FIG. 3 as viewed from a different angle; and

FIG. 3b illustrates a modification of the apparatus of FIG. 3 showing a particular relationship between the delay line helix and its supporting rods.

Referring to FIGS. 1 and 2, the helix 1 is formed from a tape-shaped conductor, for example, a molybdenum tape, and is disposed between three insulating bars 2 extending parallel to the helix axis and bearing directly against the inner wall of a tubular vacuum casing 3 of circular cross section which coaxially enclose the helix 1. In this embodiment the insulating bars are, according to the invention, hollow, i.e., tubular, such tubes 2 consisting of quartz or ceramic material dielectrically loading the helix 1 far less than solid bars of the same diameter. As a result of the small dielectric load, a higher coupling resistance for the helix line is thereby obtained.

The dielectric loading of the helix line through the insulating tubes 2 can be further reduced by the feature of providing openings in the insulating tubes between adjacent contact surfaces of the windings of the helix line 1. FIG. 3 illustrates a longitudinal section through a corresponding example of the invention, in which figure, the openings in the insulating tubes 2 are designated by the reference numeral 4. The openings 4 can also be so proportioned that only every second turn of the helix line 1 is seated on the insulating tubes 2. In this case, alternate helix contacting portions could be omitted as indicated in FIG. 3b. 1

The invention is not limited to the illustrated examples of construction. In particular it is not required that the insulating tubes rest directly against the inner wall surface of the vacuum casing as, for example, the insulating tubes may be retained in operative position by metal rings without slots or other suitable retaining means.

Changes may be made within the scope and spirit of the appended claims which define what is believed to be new and desired to have protected by Letters Patent.

We claim:

1. In a traveling wave tube including a helix as a delay line, at least three tubular insulating members extending parallel to the axis of the helix for supporting said helix and a cylindrical tubular vacuum casing enclosing said helix in a vacuum, wherein the improvement comprises the provision of a plurality of spaced-apart transverse slots in said tubular insulating rods, said slots being spacedapart along the entire length of said tube, and said helix connected to the surfaces of said tubular insulating rods between adjacent ones of said transverse slots.

2. In a traveling wave tube as set forth in claim 1, wherein each of said transverse slots are of a width such that each second turn of said helix contacts said tubular insulating rods.

3. In a traveling wave tube as set forth in claim 1, wherein said tubular insulating rods contact and bear directly against the inner wall surface of said tubular vacuum casing, said casing coaxially enclosing said helix.

(References on following page) References Cited UNITED STATES PATENTS 4 FOREIGN PATENTS 1,295,496 5/1962 France.

ES Z E HERMAN K. SAALBACH, Primary Examiner Levin et a1 3153.5 X 5 S. CHATMON, J r., Assistant Examiner Landsbergen 3153.5

Bodme'r et a1 315-3.6 U.S. C1. X.R.

Wilmarth 315-3.6 315-36 

